This invention relates generally to methods and apparatus for conveying, sorting and counting items characterized by having a thin paper or paper-like substrate, such as currency.
High speed mechanical conveyors of currency typically include some type of mechanism for counting or otherwise recording a number of notes that pass a certain point. For example, if it is desired to accurately count the notes as they pass a certain point, or after they pass the certain point, and if the counting mechanism assumes that only one note is present at a time, then if a plurality of notes are xe2x80x9cstuck-togetherxe2x80x9d or otherwise attached to one another the count will not be accurate. To avoid this problem one may provide some type of device for detecting if more than one note is present. However, due to the typical high velocity at which the notes pass a given point, the detecting device must operate accurately in a high speed, preferably non-contact manner, while avoiding the generation of xe2x80x9cfalse alarmxe2x80x9d indications that may result in the operation of the conveyor system being halted, slowed, or otherwise altered.
It is a first object of this invention to provide an improved technique to detect a presence of more than one item at a particular point along a path through an item conveyor or transport system.
It is a further object of this invention to provide a high speed, non-contact sensor that is capable of detecting a thickness of a substrate, such as a currency substrate, and for indicating a number of substrates that are present at a particular point along a path through a currency conveyor system.
The foregoing and other problems are overcome and the objects of the invention are realized by methods and apparatus in accordance with embodiments of this invention.
Disclosed is a method and system for detecting a presence of more than one item at a point along a conveyance path, comprising steps of (A) generating a light beam and directing the beam through the path such that a presence of the item will cause the beam to be attenuated; (B) detecting the beam after it is attenuated by the presence of the item; and (C) determining from the amount of attenuation how many items are simultaneously present. In the preferred embodiment the item is an item of currency, and the step of generating a light beam includes a step of operating an optical source, such as a LED or a laser, to generate a beam having a wavelength in the range of about 400 nm to about 1 micrometer or longer.
The method can further include a step of detecting light that reflects from the item of currency to determine at least one characteristic of the item of currency, such as an amount of soiling.